Every now and then I find myself wishing I had a documented copy of a clean Default Domain Policy GPO and Default Domain Controllers GPO lying around for reference.
I was setting up a Server 2016 AD lab in Azure today and thought I’d take the opportunity to save a copy of the GPO reports in HTML and PDF format while I was at it. Here they are, in case anybody’s interested:
On the odd occasion that I need to use variables within Group Policy Preferences, I sometimes find myself wishing that there was a blog post that lists out exactly what the variables resolve to.
For example, does the %ProgramFilesDir% value include a trailing backslash? Or do I need to include one myself?
Sure, you can press F3 to bring up the list of variables, but it doesn’t provide example values:
I decided to use Group Policy Preferences itself to generate a list of the variables and their values. This was achieved through the INI file extension:
I’ve exported these preference items to XML, so you can import them into a fresh GPO and test for yourself. Get the files here.
I couldn’t get the User preferences extension to generate an INI file, and ran out of time to troubleshoot, but here’s all the variables pertaining to a Computer policy (I’ve obfuscated some values):
Apologies for the image-based table. WordPress.com doesn’t make inserting tables particularly easy.
I decided to spend some of the quiet time now at the beginning of the new year to clean up Group Policy here at my new job. We had roughly the same number of GPOs as staff!
I’d already removed at least 10-20 GPOs manually, but I wanted a quick way to find all of the un-linked GPOs that were still just sitting around.
I found this great post by Mark Schill from back in 2013 that still does the job.
Mark’s solution, however, pulls out only the display name property. I needed to modify his solution a little, as I wanted to pipe the results to the Remove-GPO cmdlet. Here’s what I did:
Get-GPO -All | Where-Object { $_ | Get-GPOReport -ReportType XML | Select-String -NotMatch "<LinksTo>" }
The above one-liner gets all unlinked GPOs, and returns Microsoft.GroupPolicy.Gpo objects.
It goes without saying that you should be very careful when bulk-deleting anything. I first backed up all of my GPOs and dumped the list into text format to review it. I manually checked the settings on a few of the GPOs in question, and only then, deleted them.
Here’s how I generated the list to review:
$unlinkedGPOs = Get-GPO -All | Where-Object { $_ | Get-GPOReport -ReportType XML | Select-String -NotMatch "<LinksTo>" }
$unlinkedGPOs | Sort-Object -Property DisplayName | Select-Object DisplayName,CreationTime,ModificationTime | Format-Table
Troubleshooting a Group Policy issue this week has had me enabling the Group Policy debug log and trying to make head or tail of it.
Note: Don’t use Win32_Product. It’s not a good idea, and even Microsoft warn against using it.
WMI filtering on Group Policy Objects is an incredibly useful and powerful feature within Active Directory, but going nuts with your queries could affect your end users.
Today I came across a server that had been placed in a sub-OU by a colleague simply for the purposes of applying a GPO to it. The GPO in question was configured to make some changes to the BranchCache feature.
If the policy needs to apply to a subset of all servers in an OU, it would be cleaner to apply a WMI filter to the GPO itself rather than limiting the scope of the GPO by explicit security filtering.
Here’s what I did to clean it up:
This same strategy could be used to apply a policy to all IIS servers, all file servers, etc. The possibilities are practically limitless.
You could even filter on something like Win32_Product to apply a specific GPO to Exchange servers, for example.
SELECT * FROM Win32_Product WHERE name = 'microsoft exchange server'
Don’t use Win32_Product. It’s not a good idea, and even Microsoft warn against using it.
One good use of Group Policy Preferences is in controlling Windows Services. You can read how to do so here on Alan Burchill’s site, as it’s the same method that I use.
I sometimes go one step farther, and only apply that preference item if the service actually exists. “How do you do that?”, I hear you say. By using Item-Level Targeting and a WMI query.
One instance where I’ve used this previously is to control Adobe’s auto-update services. If the service doesn’t exist on a machine for one reason or another, the event logs will be full of errors like this:
The computer 'Disable Flash Player Update Service' preference item in the 'Policy Name Here {00000000-0000-0000-0000-00000000000}' Group Policy Object did not apply because it failed with error code '0x80070424 The specified service does not exist as an installed service.' This error was suppressed.
To test if the service is installed, first find out the Service Name, as opposed to the Display Name. That’s what we’ll use in the WMI query.
Then, apply the following WMI targeting query:
| Query | select * from win32_service where name = “AdobeARMservice” |
| Namespace | Rootcimv2 |
| Property | Name |
| Variable Name |
The targeting editor should look like this afterwards:
There’s a great article on the Microsoft AD team blog about configuring the authoritative time server automatically via group policy and WMI filters. This may save you from domain time sync issues if your PDC emulator role eventually ends up moving to a different server.
Their article covers how to set up the WMI filter, but doesn’t address the settings for NTP. Those are listed in detail under this support note.
These are the settings I’ve implemented in my GPO using Admin Templates->System->Windows Time Service:
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeConfig] "MaxNegPhaseCorrection"=dword:00000708 "MaxPosPhaseCorrection"=dword:00000708 "AnnounceFlags"=dword:00000005 [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeParameters] "Type"="NTP" "ntpserver"="au.pool.ntp.org,0x1" [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeTimeProvidersNtpClient] "Enabled"=dword:00000001 "SpecialPollInterval"=dword:00000384 [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeTimeProvidersNtpServer] "Enabled"=dword:00000001
Just saw this note whilst browsing the help on Drive Maps in Group Policy Preferences:
You can use a Drive Map preference item to configure the visibility of a physical drive rather than a mapped drive. To do so, select the Update action, leave the Location field blank, select the drive letter of the physical drive, and then configure the Hide/Show this drive and Hide/Show all drives options.
So, to hide “A” drive (in this example), you’d configure the dialog box as follows:
I didn’t know this was possible. This may come in handy one day, if you want to hide something like an OEM partition that has had a drive letter assigned.
Had a problem today where a printer driver became corrupted on our print server. This, in turn was causing the Print Spooler service on the workstations to crash repeatedly. I was unable to delete the mapped printers through the normal Printers and Faxes/Printers/Devices and Printers interface because the spooler kept crashing.
As part of the investigation process, I first used Group Policy Preferences to set the recovery options for the Print Spooler process on each workstation to always restart:
The resolution for the problem is quite a brute-force solution as the problem was confined to only a few workstations. If the problem had been more widespread, I would have narrowed down which dll was causing the problem, and then removed it via GPP using the “Apply once and do not reapply” option or via a PowerShell script.
What I then did was re-install the latest printer drivers for each of the printers that I suspected to be the cause of the problem. This is done on the print server by going to Control Panel, Printers and Faxes, File menu, Server Properties, Drivers tab. You can then select the printer driver in question and click the Reinstall button.
The solution on each workstation was as follows:
Go to Start, Printers, and verify that they’re all there. The Print Spooler service should no longer crash upon viewing the mapped printers. Some printers may have a status of “opening” for a while as they need to re-download their drivers from the print server.
User Error 